Diagnostic Value of Sonoarthrography in Rotator Interval Imaging: A Comparative Study Using MR Arthrography as the Reference Standard.

OBJECTIVE: To evaluate the diagnostic value of sonoarthrography (SA) for the superior glenohumeral ligament (SGHL) and long head of the biceps tendon (LHBT) in the rotator interval (RI), and to compare its performance with ultrasonography (US) and magnetic resonance imaging (MRI), using magnetic resonance arthrography (MRA) as the reference standard. METHODS: A total of 63 patients with suspected pathologies of the RI were evaluated prospectively. Each patient underwent conventional shoulder US and MRI without intra-articular contrast solution injection and SA and MRA following the injection of an intra-articular contrast solution. Two independent observers evaluated the detectability and pathological characteristics of the SGHL and the LHBT. Diagnostic performance was quantified based on sensitivity, specificity, and accuracy, while interobserver agreement was determined through kappa statistics. RESULTS: According to the first and second observers, the sensitivity and specificity values of US, SA, and MRI in the evaluation of LHBT pathologies were 77.3% and 86.4%-100% and 100%; 90.9% and 95.5%-100% and 100%; and 100% and 100%-100% and 100%, respectively. For SGHL pathologies, the corresponding values were 41.9% and 64.5%-96.9% and 100%; 71% and 74.2%-100% and 100%; and 58.1% and 58.1%-93.8% and 100%, respectively. The interobserver reliability was almost perfect for SGHL (κ = 0.896; 95% CI: 0.782-1.000) and almost perfect for LHBT (κ = 0.964; 95% CI: 0.894-1.000). For SGHL, SA significantly outperformed US in the less experienced observer (exact McNemar p = 0.0039; AUC 0.823 vs. 0.632, DeLong p = 0.0002) and exceeded MRI on AUC comparison in the more experienced observer (0.839 vs. 0.758, p = 0.048); interobserver agreement with SA (κ = 0.896) was markedly higher than with US (κ = 0.602). For LHBT, SA was numerically superior to US and comparable to MRI. CONCLUSION: Sonoarthrography is useful for assessing the RI, improving sonographic assessment of the SGHL and substantially reducing interobserver variability compared with conventional US, while maintaining comparable accuracy for the LHBT. This technique can serve as an alternative when MRI is contraindicated or unavailable. ADVANCES IN KNOWLEDGE: The rotator interval is a complex triangular region located in the anterosuperior aspect of the glenohumeral joint. The cohesive stabilizing role of its anatomical components is critical for maintaining passive stability. Ultrasonography may not consistently provide reliable visualization of the deep ligamentous structures within the rotator interval. Sonoarthrography has a high diagnostic accuracy in the assessment of rotator interval structures.